unicorn 4.5.0pre1 - check_client_connection option

unicorn 4.5.0pre1 - check_client_connection option

The new check_client_connection option allows unicorn to detect
most disconnected clients before potentially expensive
application processing begins.

This feature is useful for applications experiencing spikes of
traffic leading to undesirable queue times, as clients will
disconnect (and perhaps even retry, compounding the problem)
before unicorn can even start processing the request.

To enable this feature, add the following line to a unicorn
config file:

  check_client_connection true

A huge thanks to Tom Burns for implementing and testing this
change in production with real traffic (including mitigating
an unexpected DoS attack).